But if that's what they did, it's going to piss a whole lot of people off and they had to know that going in. It's not the kind of "twist" ending that leaves people thrilled, but rather the kind that leaves them disappointed and confused as to why the writers would do something so lame. [e.g., Bane being Talia's lackey in TDKR.]

Spoiler!!! Click to Read!:

Only because Talia was awful and did nothing. If they develop Killian as a total badass and build the film around him, instead of shoehorning him in, then it'll work quite nicely

And I don't think it means Mandarin can't be interesting and well characterized on his own terms. But it's definitely not the Mandarin people were expecting.